I assume you're using 11t. This happens sometimes with cps when they're undone. It seems to be a bug.
But in general, you really don't need to adjust bias handles. In the majority of cases, the existing geometry is fine. Adjusting the handles also produces unpredictable animation.
When you say the model changes.....does it look more blocky or something like that? It might be the realtime resolution that's putting you off. Press PageUp to get incrementally better resolution. Also, you should render it(Press Q) to see what it's really looking like.